Normalized elipse Head

[petroPV]

For fatigue service reason, we call out vessel material to be normalized SA 516-70, and elipse heads (min thickness 2") get to be hot formed. The vessel fabricator proposes to use normalized plates to hot form the elipse heads and normalize the heads after.
My concern is if the mechanical properties of SA 516-70 plates are impacted by twicw normalization. The plate MTR only shows simulation test results of two cycles PWHT. But I only feel confident if MTR shows normalization simulation test results. My understanding is that multiple normalizations (even PWHT) may soften steel, decrease strength (or hardness).

Since EFE% is over 5%, I am wondering if vessel fabricator has to heat treat the head again per UCS-79 after head normalization. I would think the normalization heat treatment can perform the stress relieving function also (?). If this is true, then it's not necessary to heat treat the head again after head normalization.
I believe we have many matallurgists here.

 

[petroPV]

I always thought there are several material engineers in this forum. Maybe I remember wrong.

 

[DVWE]

They probably have already seen your other same post in the Boiler and Pressure Vessel forum.

 

[tr1ntx]

Or if not try the Metal & Metallurgy Engineering forum.

 

[gr2vessels]

petroPV,
I'm not metallurgist, but I know that the heads have to be normalised after forming and again after welding it to the shell (obviously, based on the thickness). I also know that in many cases the heat treatment has to be repeated if the properties have not been achived in the first case and the 516-70 can take several normalizing HT without damage to the structure.
Cheers,
gr2vessels